Navigation calculator

ABSTRACT

A navigation calculator comprising a base plate having angular markings, a plurality of round members rotatably mounted on said plate and on each other, each of the round members being adapted to be moved to insert the navigation parameters such as magnetic variation, compass deviation, compass reading, current direction and wind direction so that the various parameters are added to give a final reading. A pair of protractor arms are adapted to be rotatably mounted on top of the stack of round members for drawing a course on a chart.

ijite States atent Banner M lMarch 20, 1973 [54] NAVIGATION CALCULATORFOREIGN PATENTS OR APPLICATIONS Inventorr Philip Banner, 28 Oxford Road,28,684 3/1918 Norway ..33/7s R Massapequa, NY. 11758 13 PrimaryExaminer-Robert [52] US. Cl .Q ..33/1 SD, 33/356, 235/78 [51] Int. ClG0lc 21/20, G06c 27/00 [58] Field of Search ..33/1 SD, 75 R, 224; 235/78[56] References Cited UNITED STATES PATENTS 499,087 6/1893 Baker..33/224 X 2,904,885 9/1959 Wood ..33/75 R X 2,105,103 l/l93 8Sinitzin-White ..33/l SD 2,548,319 4/1951 Osterberg ....33/l SD UX1,226,141 5/1917 Sterling et al ..33/75 R 2,545,935 3/1951 Warner ..33/]SD UX [5 7 1 ABSTRACT A navigation calculator comprising a base platehaving angular markings, a plurality of round members rotatably mountedon said plate and on each other, each of the round members being adaptedto be moved to insert the navigation parameters such as magneticvariation, compass deviation, compass reading, current direction andwind direction so that the various parameters are added to give a finalreading.

A pair of protractor arms are adapted to be rotatably mounted on top ofthe stack of round members for drawing a course on a chart.

3 Claims, 9 Drawing Figures D O ,p RIATIO PmNn-mmzomza 3.721.007

- summ 4 FIG! Q i w a w VMM N 2 INVENTOR PHILIP M- BANNER PATH-1150mmI973 SHEET 2 OF 4 I FIGS FIG. 4

- AINVENTOR. PHBLIP M, BANNER PATENTED MAR 20 I975 SHEET 30F 4 STARBOARDEAST PORT WEST 2 INVENTOR.

PHILIP M BANNER PATENIEUMAR20 I975 SHEET u of 4 FIG 7 M 0 l T A m A vIFIG8 FIG 9 r': INVEN TOR.

BY PHILIP M.BANNER NAVIGATION CALCULATOR This invention relates to anautical navigation calculator that incorporates various methods ofassistance to navigators, particularly to small boats, ships andairplanes and wherever magnetic compass equipment is used. It has beendesigned to facilitate rapid reading of important information relativeto marine or air navigation and assisting in various teaching methods. Toften, the operation of a boat becomes a responsibility where thenavigator is confronted with a last minute crisis, necessitating animmediate analysis and decision regarding safety, direction of travel,winds, currents, deviation and variation, position finding, distanceplotting, and other factors which are all embodied in this calculatorand inseperably a part of basic navigation.

The calculator will help those seeking to acquire the art of navigationat a time when we have 47 million registered boats in the United States,and the number keeps increasing rapidly in this leisure recreationalsport of boating. No one can really expect the inexperienced small boatoperator or skipper of a new sailboat to have the expertise or traininggiven to the professional navigator in airplanes or ships, but thenumber of small craft accidents and equipment damage resulting from poornavigational habits suggests an immediate need to educate or re-educatethe operators. Faster operating equipment and the greater interest inspeed adds to the difficulty where in some cases boats have proceededtoo far, entered dangerous areas, gone aground on bars, traffic problemsdanger resulting from lack of knowledge of rules of the road, or justdid not have a simple practical way to calculate the deviation and otherfactors which this instrument does, besides providing means of doublechecking the information. This calculator offers an efficient coursefinder wherein the course arms easily make it apparent which course isrequired. The two course arms have been bisected to allow both of itsinside edges to represent the true center line while any movement of onepart from the other automatically measures the amount of movement indegrees. As I will point out and explain, it also assists the navigatorwith marine rules of the road-rules concerning lights at sea andposition finding through bow and beam bearings. It allows a simpleanalysis of different courses, compass, magnetic and true bearings,showing effect of wind and currents upon the course of movement. Itsbase has been designed to meet the specifications of accepted form ofplotting procedures.

The base has a lubberline for plotting. One method features the pointsystem, where the value of each individual point is l 1% and there are32 points around a compass. This corresponds to the use of trigonometryin position finding methods, drift calculation, safety and lighting atsea as referred to by all present or old accepted standards ofnavigation. I refer to American Practical Navigator (Bowditch),published by the U. S. Naval Oceanographic Office, or C. Chapman M.E.,whose works are published in Motor Boating Courses. Another part of thebase has the 32 points clearly marked completely around its periphery,allowing their use on both halves of the different parts. The other partof the base has been marked differently to conform to the present methodof accepted course plotting also. Reference is hereby made to theVictory Leeway Calculator, where table 1 Bowditch shows angularity ofone to four point courses for distances as far as one is likely to usein the ordinary along shore navigation. The base of this calculatorfacilitates this operation while the other part serves equally anotherimportant function in adherence to points used in position findingthrough bow and beam bearings. All magnetic compasses are divided into32 equal parts, each having a name representing 360.

These and other important features of the invention will now bedescribed in detail in the following specification, naming each part anddescribing its function as shown on the drawing, then pointed out moreparticularly in the appended claims.

A principal object of the invention is to provide new and improvednavigation calculator means for a craft.

Another object of the invention is to provide new and improvednavigation calculator means which are simple in construction, and whichprovide means for adding navigational parameters such as magneticvariation, compass deviation, compass reading, current direction, andwind direction, so that all of said parameters are added upautomatically to give a final reading.

Another object of the invention is to provide new and improvednavigational calculator means for a craft comprising a base plateadapted to be mounted on a craft, said base plate having angular indiciaradiating from the central point of said base plate, a first roundmember rotatably mounted on said base plate on said center point, saidfirst round member having angular indicia thereon, a second round membersmaller than said first round member rotatably mounted on said firstmember, said second member having angular indicia.

Another object of the invention is to provide new and improvedprotraetor arm means which are adapted to be rotatably mounted on top ofthe calculator for locating and drawing chart courses.

These and other objects of the invention will be apparent from thefollowing figures, of which:

FIG. I shows a plan view of the calculator.

FIG. 2 shows a cross-sectional view of FIG. 1.

FIG. 3 shows a top view of the protraetor arms.

FIG. 4 is a detail view of bolt securing means.

FIGS. 5 and 6 are diagrams illustrating the use of the invention.

FIGS. 7, 8 and 9 are detail views of the dials (omitting the cutouts).

Problem: Example No. 1, FIG. 5

True course is desired. Compass course is 45. Deviation is 15W.Variation is 12E. Wind is from the West Current is from the East 90".Current magnitude equals wind magnitude effect.

Procedure: Example No. 1 (containing the unusual variable of variationand deviation being in different directions) I. Set dial assembly socompass dial E reads 45 on base H.

2. Set dial F (magnetic deviation bearing) so that the Problem: Example2, FIG. 6

Compass course is desired. True course 110. Variation E. Deviation 12E.

Procedure: Example No. 2

1. Set dial F to 110.

2. Set dial E the same as F and then rotate readout on starboard side(east) until the combined total of both factors variation 15 anddeviation 12, total of 27 reads in E dial (compass).

3. Read answer on E dial lubberline 83.

Course Arms A and B When arms A and B are used, B is placed over thelubberline and A is utilized to find courses, make corrections, plotwind and currents while any angle between the two is recorded on thebase of these parts in degrees. This calculator provides a triple checkof data: 1. by degrees or directions on dials; 2. by readout informationon all dials in degrees; 3. by the arms A and B which can determine thedegree of angle and triple check all information.

Suppose we are on a boat headed east. The compass dial E is set on thelubberline L to the arrow on the base. Next you turn the deviation dialF (magnetic bearing) to the proper allowance by referring to a deviationchart, if available, or by the use of the plotting arms, finding fixedreference on shore or at sea, and measuring same on the degree scale ofthe arms, then placing this information onto the deviation scale. Now wemust refer to a navigation chart and determine the variation and placethis dial G properly on the lubberline also. You will take note thateach of the dials E, F and G have readout on both the port and starboardsides, therefore measuring every movement of each of these three dials.Now that we have lined up the three dials associated with the compass,we can adjust our course by the number of degrees of difference shown inthe readout boxes provided. Suppose deviation were 15 port and variationwere 12 starboard. This example would be handled by subtractingvariation from deviation and finding a remainder of 3 port side. Theadjustment for a true course is made to the boat compass by 3 port sidewhich changes the heading of East to 3 to the North.

Suppose you are heading the craft northeast by the boat compass and youwish to head north. You turn the calculators compass dial E until thereadouts show zero and you are now on a north compass course. Inchanging the deviation, the same rule is applied. You can use thelubberline L or the readout, whichever is most convenient for thenavigator.

Suppose we are headed northeast and the plotting arms A and B, FIG. 3,are placed over the direction of travel and in scanning with these armswe find that the apparent course is 45 easterly. This is read on thepart of the plotting arm A, and we now change each dial accordingly. Ifthe deviation and the variation are the same as when northeast, we willnow be heading north. Each of the dial readouts will be back to zero.

In using the base containing the point scales, we can now find ourposition by the bow and beam method. Reference is directed to Piloting,Seamanship and Small Boat Handling" 1969-70 edition by Chas. Chapman,M.E., published by Motor Boating, page 352 (i) wherein BOW AND BEAMBEARINGS or DOUBLING THE ANGLE ON THE BOW both refer to the beam method.Further example is hereby directed to a simple position locator, easy touse, and merely requires a knowledge of points. Figure 218 page 115Volume V by Chas. Chapman, M.E. refers to an easy method of applying thecompass points to position locating. Bow and Beam bearings can best bedescribed as successive relative bearings (right or left) of 45 and of afixed object.

When using all the parts of this invention, additional scales becomevery useful in assisting the navigator. After the compass, deviation andvariation factors are placed, the pilot can set the wind and currentdials according to the direction they are coming from and affecting thedirection of the craft. Suppose you are on an easterly course. Youdetermine the wind being from the west, you add the estimated effect ofthe speed to the speed of your boat, and note that the direction of thewind will not affect your course sideways. Next you set the currentdial, for example, from the east. You then deduct the speed of thecurrent and note that it is coming from the direction you are travelingand watch for changes. If the current or the wind were coming from anyangle, the estimation would be made to change the course accordingly. Inany event, the wind and the current are two very important factors whichmust be considered by the pilot in determining his course. In thisarrangement of information, this invention calculates all the factorsnecessary to facilitate safe travel. The base H contains a point systemthat can be utilized for wind and current plotting.

The plotting arms A and B contain a safety feature. The arm A hasimprinted upon it a pattern like that used in Rules of the Road". Tenpoints to the right of the bow are red colored to designate the dangerzone. This is from the dead ahead position to 2 points abaft thestarboard beam. A boat is divided into 32 equal parts and each has aname. Although it is nice to know all the names, the most important arethose from dead ahead to 2 points abaft (behind) the starboard (rightside) beam. These 10 points are known as the danger zone. Any boatcoming towards your danger zone has the right of way, and you must keepout of his way. At night your green light shows through this zone. Inaddition to this, am A has a line drawn on the port side to show 10points where the red light shows when lit. White bow lights are requiredfor 20 points and a white light at the stern is required for all 32points. The base of this invention specifically shows the points at all32 places where they belong and this too will allow a pilot toimmediately determine the safety and lighting of vessels.

I would like to point out the importance of the readout facility offeredby this invention. Whether either side of the base is used, thedifference of movement of dials E, F, G will show in degrees the amountof movement. This is also accomplished by comparing each of therespective dials and their position in degrees, and this is also checkedagain by the course arms A and B. Therefore, this invention can actuallycheck out these important calculations three ways.

The arms A and B are quite different from those of the prior art in thatthey measure an angle or a course from either of the inside edges.Instead of having to use a sharp point to denote (mark) center or to seethe center in the middle of an arm and making the second mark, youmerely use either arm for present course and set the other arm forapparent course and either edge will display the true center for markingpurposes. This offers a simplified method and in addition to all this,the arms A and )8 record a reading of degrees of difference between thevarious positions they are placed in up to any number of degrees thatmay be required. For illustrative purposes, 45 have been shown.

The drawings illustrate the navigational calculator shown in F116. l.The device will consist of a heavy plastic base H upon which are mountedfive concentric circles C, D, E, F, G and having mounted on top twocourse protractor arms A and B. The joining of the above stated partsmay be accomplished by use of grommets or other like means K and a boltL and nut designed to keep all the parts in close tolerance. The partsof this invention would be best suited by being made out of plastics orother economical means that would resist dampness and other conditionsaround the water.

in FIG. 3, arm A represents one of the course arms that measure coursechanges in degrees. it has an imprinted nautical scale upon it,corresponding in miles to the various distances and scales used on allnavigational maps, produced by the U. S. Department of CommerceEnvironmental Science Service Administration and by the MacMillan MarineAtlas. interest is directed to the particular instances which includethe normally used scales-l/80,000, l/40,000, 1/20,000. Arm A is termedthe primary arm because it contains a scale in degrees on its baseshowing the exact degree of difference between the measurement made byboth arms.

Arm B is the secondary arm which when moved exposes the number ofdegrees difference between the two arms. if used separately or betweendifferent measuring points it provides an alternate (apparent) coursefor the navigator.

Arms A and B are secured together by a grommet or rivet, or grommetedwith all the other parts as to permit free and accurate movement. FIG. Ashows a bolt L assembly so designed to permit all of the plasticconcentric circles with the arms A and B to be locked together. Itcontains a shoulder and cap-nut and can be tightened by spacing washersand a spring. This would permit removal of arms A and B from the rest ofthe calculator for drawing purposes or for individual use formeasurement of angles on different course plotting.

Arms A and B, FIG. 3, were designed to permit maximum plotting area byhaving the leading edges facing each other, not to interfere withdrawing a second line and not having to move the instrument toaccomplish this; also not having to place point markings nor mark thecenter points of protracting arms which are usually required on presentdevices. Both arms when in a closed position will equally share the sameline as if drawn from either one. This allows greater accuracy inplotting an apparent course. Having leading edges abutting and facingeach other allows greater use of the arms A and B in that the two armsdo not overlap, wasting valuable plotting area. Another importantfeature of the arms A and 1B assembly is its capacity to measure thedifference in angle between the arms at any points that it may be placedaround the 360 of the compass. it

can also be used to measure the points at 11% markings around the 360scale on base H that may be used in coordination with locating position,allowing for wind or currents where point systems are used. As one armintersects the other, it measures an angle. Therefore, this would permitunrestricted use in measurement of directions, deviation, distances andspeed as well as other uses afforded by this calculator.

Arm A contains a safety dial conforming to points used in Rules of theRoad and boat lighting requirements by points. In addition to this, itshows the danger zone where others have the right of way. Knowledge ofthis, particularly keeping this information in front of people willacquaint and remind them to observe the navigation rules.

FIG. 1, Dial C, Wind Leeway is the leeward motion of a vessel due towind. It may be expressed as distance speed or angular differencebetween course steered and course through the water. However expressed,its amount varies with the speed and relative direction of the wind,type of vessel, amount of freeboard, trim, speed of the vessel, state ofthe sea and depth of the water. Leeway is most conveniently applied byadding its effect to that of the current and other elements introducinggeographical error in the dead reckoning.

Specifically, dial C actually shows the two important reference pointsin the form of arrows designating where the wind is blowing from andwhere it is blowing to. in order to calculate the effect of wind, firstset the compass and deviation and variation dials properly, then alterthe setting according to the estimated effect of the wind upon yourparticular vessel. This information will immediately bear significanceto the user, who usually measures or estimates the effects and isreminded to make this valuable computation. Reference is made to table 1of Bowditch, the navigators bible, showing angularity of one to fourpoints for courses one is likely to use in alongshore navigation. It isintended as an aid for quick calculation of the allowance to be made forany force such as tide, wind or sea, which will tend to set the shipsideways on her course and can be used for ordinary amount of leeway fordistance up to 25 miles or on a per hour basis for longer distances.

FIG. ll, Dial D, Current This is also unquestionably another valuablecalculation the navigator must render. According to present practices,the following would denote an entire common sense approach to be usedwith this dial D, which rapidly determines for wind allowances. Dial Dshows the direction of the current, where it is flowing from and whereit is flowing to. A navigator could estimate rather closely byobservation the effect upon his vessel. For example, suppose you areheading north and the current dial shows the current from the west, onewould easily observe on dial D the obvious effect. Even if the currentwere oblique from any direction and the navigator could estimate thecurrent speed and the boat speed he would effectively estimate theresult.

There are two factors in this calculation, one the real course, and theother the apparent course, which will compensate the effect of currentor wind pressure on the boat. However, for those who prefer a formulafor speed current ratios and charts, they are available. This systemuses the point method to determine course allowance for currents.

FIG. 1, Dial E, Magnetic Compass This dial relates to the magnetic boatcompass, designating cardinal and intercardinal points on a 360 scale.The compass shows the direction of heading. Its center is always in linewith the keel or lubberline L. This magnetic compass when used withother parts of this calculator provides a means of correcting magneticbearing caused by polar deviations or by influences within the ship,such as the use of the wrong type of compass such as an airplane compasson a boat, chrome plating causing a magnetic field, steel or electricwelding near the compass, improper installation of electrical equipmentnear the compass, untwisted or shorted wiring, improper storageprocedures, etc. A magnetic compass is subject to inherent limitationssince it responds to any magnetic field. It is also affected by thechange in the local magnetic situation. The undetected presence orchange in position of magnetic material near the compass may introducean unknown error. Thus, an error may be introduced by a steel wrench ora paint can left in the vicinity of the compass. A pocket knife or smallkeys are sufficient to affect the compass if brought as close as theyare when on the person of an individual standing by the compass. Nylonclothing may introduce an error, the earth's magnetic field, etc.Another consideration of importance is the positioning of a marineengine or engines where installations of iron and steel affect thecompass in each direction differently. The navigator places the compasson the calculator in line with the lubberline arrow, according to thedirection shown on the boat compass. This part E has two sight holesconveniently located in both port and starboard sides. This will showthe degree of movement on this dial from the center position. If onewanted to move this compass for any adjustment or allowance it could beaccomplished by moving it until you reach the desired amount of degreesshown in the sight hole, or by watching the degree marks upon the outeredge of the compass dial. The information seen through the sight holesare the corresponding numbers on the next dial F.

FIG. 1, Dial F, Deviation This is the magnetic bearing. It is a compassrose having the same design, information and significance as dial E,having a 360 scale and cardinal and inter-cardinal points. Theexplanation given referring to dial E dealing with interferences thatcause deviation are all regarded as the deviation factors where there issuch great difference between the magnetic compass and the magneticbearing. Once the deviation is known, it is then applied to thisdeviation dial. This part also has two readouts that are imposed on thedial G, the next dial under it. It can also be adjusted by the readoutin degrees. If the pilot does not have a deviation recorder, he willtake a fix on different objects which will correct the deviation. Manyboats are equipped, and all using a magnetic compass should be, with acompass deviation card where the angle between the magnetic meridian andthe axis of a compass card is recorded. Finding the deviation is bestaccomplished with the vessel on magnetic headings. The compass beingadjusted cannot be used for placing the vessel on a desired magneticheading because its deviation is unknown, and is subject to changeduring the process of adjustment. A number of methods are availableincluding use of (1) another magnetic compass of known deviation, (2) agyro compass, (3) bearing of a distant object, (4) azimuth of acelestial body. Magnetic compass deviation at the desired magneticheading is determined from the deviation table for that particularcompass and applied to the magnetic heading to determine the equivalentcompass heading. If the deviation on some headings is large, the desiredaction is to reduce it, but if this is not practicable, a separatedeviation table for compass heading entry may be useful. This may bemade by applying the tabulated deviation to each entry of magneticheading, to find the corresponding compass heading, and theninterpolating between these to find the value of deviation at eachcompass heading. Thus, deviation is the angular difference betweenmagnetic north and compass north.

Example: A vessel is on a course 225 true, the deviation is 2 west, thevariation in this area is 88 west;

2 deg.W deviation 235 deg.compass heading, turn dial E to Arms A and Bare then used to scan the map for double checking or new course.

Compass error is 8 W plus 2 W equals a total of 10 W. It is well to bearin mind the result of sailing off course. With a 10 error, the vesselwill be set off course 1 mile for every 5.7 miles run. This would beserious when making a landfall in poor visibility. More hazardous arethe risks of stranding when running a narrow channel through shallowwater in fog or or heavy rain. The small craft sailor is constantlyoperating his craft in narrow channels and very shallow areas where thepreciseness of navigation is required to avoid equipment damage orsafety in passing through such areas, where deviation and every factorbecomes important. Today there are more and more pleasure boatsresponding to the art of taking trips, sometimes to far off islandswhere variation anddeviation and true headings are absolutely necessaryto safe journey. Electric windshield wipers can cause a drastic changewhich must be taken into consideration with other items causingdeviation.

FIG. 1, Dial G, Variation This partially marked dial, showing 45, ormore if desired, represents the course relative to true north, thedirection of the north geographic pole. This calculator has now madethree references to direction, on three different circular discs, E, F,and G, plus the effect of current and wind dials D and C, which alsoeffect the line of travel. The subject of deviation concerned itselfwith dials E and F. Now we are concerned with compass error, which isthe angular difference between true north and compass north (thedirection north as indicated by a magnetic compass). The angle betweengeographic and magnetic meridian, compass error and variation are thesame. The three methods by which bearings may be expressed are:

1. True: when they refer to the north geographic pole;

2. Magnetic: when they refer to the north magnetic pole. To changemagnetic courses to true courses, the former must be corrected forvariation Dial F (deviation, or magnetic bearing);

3. Compass: when they refer to the particular boat compass on eachparticular heading and must be corrected for both deviation Dial F andvariation, Dial G, for conversion to true bearings or true courses.

The earths lines of force do not run as great circles passing over theearth and through the magnetic poles but change their direction over theglobe, making many different angles with true meridians. Hence,variation differs with locality and the navigator musttake into accountthe change in variation as he proceeds upon the voyage. For example, onthe course of the great circle from New York to Liverpool, the variationchanges over 10 in 600 miles. Off the coast of Florida, the variation iszero. An aviator or boat operator departing from Florida to Nova Scotiawould, if he failed to take the change in variation into consideration,find himself not in Nova Scotia, but lost in the woods over Maine.Variation not only changes with locality, but generally changes itsvalue slowly in any given place. In piloting and small boat handling,the mariner finds upon the chart not only the value of the variation,but the rate, the amount and direction of the annual change given uponthe compass rose. By checking a chart or determining a fix of shoreobjects the mariner can adjust his direction accordingly, and proceed ona safe journey with minimum loss of time. This particular part of thecalculator, dial G, can save time in figuring a course where usually thepilot must refer to the charts for true bearing, when here it is indexedin rotation, like the rose on the charts, offering a complete picture tothe navigator. Even after being removed from the map area, thecalculator serves the pilot with the recorded information for furtherreference analysis while enroute. The variation is determined byreference to local charts and the operator of the calculator adjusts thetrue north disc G, FIG. ii, to the left or right of the centerline mark(lubberline) according to the number of degrees of variation easterly orwesterly or port or starboard. This dial G, FIG. ll, having a 90 scaleupon it interpolates with the other scales for exact measurement indegrees. It is broken down to two 45 scales, one on each side of thelubberline. You will note the readout facility also afforded to thisdial G as to E and F. The information is printed on dial H, FIG. 1 asseen at the cut out portion of dial G.

FIG. 1, Dial H, Calculator Base This base consists of heavy plasticmaterial plate upon which are mounted the five concentric discs and thecourse plotting arms A and B, FIG. 3, each earlier discussed in partsrespectively. This base serves more than one purpose. It has a directionpointer indicating the lubberline L and direction of travel and alsoserves as a reference point to all the scales of this calculator. It canbe made of several materials, preferably a transllfl parent plastic thatwill allow greater view of map surfaces it is projected upon. Whatever avendor may require in materials will not change the informative values.

Reference is hereby directed to the ll% points at their proper placesaround the entire 360 scale of the compass being printed upon the basematerial. This will aid in safety bearings, lighting rules at sea,position locator methods using bow and beam measurements, wind andcurrent plotting procedures, etc. These 32 lines and markings are allimportant to the use and operation of the compass.

This base H, FIG. 1, features another object of the invention beingdifferent from all other plotting bases in having two methods ofcalculating and plotting courses. FIG. 1 shows the part marked on topport and starboard as having the lines of each point for being carriedto the outer part of part H. This will make using the point system veryconvenient, where the lines are drawn over the conventional plottingsquares.

This dial l-I, FIG. 1, also shows a second arrow of travel at the otherside of what has been outlined above, having a standard plotting base.If the navigator decides to use either of the two methods he will stillread the degrees of difference in the same readout boxes provided ondials E, F and G, FIG. 1. This information is so arranged on the properdiscs as to provide continuous reading. If the navigator still wishes touse the point system on this part, the points are each shown at the endof short lines that are symmetrical to the center line of thecalculator. Therefore, anyone desiring to plot a course with eithermethod merely places arms A and B, FIG. 3, in any desired position andreads the nautical miles on the arms A and B, and reads out the degreeof change between any movement in the arms, which are designed to permita centerline drawn between them.

The port and starboard reference is to the left and right when lookingforward to the bow. They are expressions easily understood andstandardized. By using the first or second position of the arrows oftravel, all the parts of this calculator will be directed to the waychosen and will bear the same accuracy either way. Using wind andcurrent charts, positioning methods all refer to the point method, thathave been published for years and used widely by mariners everywhere.

Grommet K secures the various members together, allowing freedom ofturning to permit calculations. Where grommets are used (as opposed toanother method, or a rivet) it will be accompanied by a bolt or screwarrangement to fit the diameter of the grommet properly and having ashoulder that ends at a point where the five discs end. This b'olt wouldthen also have an extended thread to permit locking of the arms parts Aand 18, FIG. 3, together on the calculator. The arms already have agrommet and the bolt is of the right size to permit the correcttolerance allowing proper turning. The bolt could also be of a type madewith a snap lock to facilitate the locking of the arms parts A and B,FIG. 3, to it accordingly. My opinion is the method serves best thatemploys a bolt as described.

Bolt assembly L is a bolt of proper diameter to fit the underneath flatside with minimum protrusion and having enough shank to fit the manyparts herein and having a thread and nut or other locking method tosecure the arms A and B, FIG. 3, to the base part H, FIG. 1, through thegrommet K, FIG. 1.

Summary Each part has been illustrated and explained functionally and,further, we have identified the use of this invention with safety: shiplighting, having two arms allowing calculation of movement of each parttherein and having two drawing surfaces representing the center lineaccordingly, having mileage scales on it conforming to scaled mapswidely used, correcting magnetic bearings, correcting compass coursesand deviation, correcting variation for finding true bearings, usingpoints of the compass as on a bearing board having a value as toposition finding, wind and current plotting and facilitating the safetydisc, having two choices of base components each having its value to anavigator, that can be used for boating or air navigation or wherever amagnetic compass is employed.

It should now be apparent that the broad teachings are applicable to anunusually wide range of information and arrangements for coordinatingnavigational data. This calculator embodies a two arm protractor thatwill assist the professional in his duties to lay courses and makemeasurements. All the parts have been described covering every singlephase of important operations a navigator would regard as novel andhaving great utility.

It is obvious that minor changes may be made in the form andconstruction of this invention without departing from the spiritthereof. Naturally, it is desired to include all changes as come withinthe scope claimed.

1 claim:

1. A navigation instrument comprising in combination: a transparent flatbase member having a central pivot hole and inscribed with a set ofrectangular grid lines, -a set of lines extending radially of said pivotcenter toward the periphery of the base member and providing thedivisions of a full circular angle scale numbered in nautical points, alubber line mark and a diametrically opposite index mark on said scale,and two arcuate degree scales inwardly of said circular scale andconcentric therewith, extending from respec tive zero points at 45 tothe left and right of said lubber line mark;

a first disc member concentrically pivoted to said base member and ofradius less than said circular angle scale and overlying said arcuatedegree scale and marked at its periphery with a scale graduated indegrees including a zero mark to which magnetic variation may bereferred and having two symmetrically placed cutouts at 45 right andleft of its said zero mark and at a radial distance from said pivot holefor reading on respective ones of said arcuate scales the relativedisplacement of said first disc member and said base member;

a second disc member concentrically pivoted to said base member andoverlying the central circular area of said first disc member that isinwardly of the cutouts in said first disc member, said second discmember being marked with a peripheral scale graduated in degrees andhaving a zero point to which magnetic compass deviation may be referred,and said second disc member havingltwo arcuate degree scales inwardly ofthe perip eral scale thereon and concentric therewith and extending fromrespective zero points at 45 left and right of said zero point of saidperipheral scale thereon;

a third disc member concentrically pivoted to said base member andoverlying a central circular area whose periphery is between saidperipheral scale on said second member and said two arcuate scalesthereon, said third disc member being marked with a compass rosecomprising a peripheral scale graduated in degrees, and having twosymmetrically placed cutouts at 45 right and left of the north point ofsaid compass rose and at a radial distance from said pivot hole forreading on respective ones of said arcuate scales on said second discthe relative displacement of said third disc and said second disc; and

a pivot element extending through the pivot hole in said base member andthrough coaxial pivot holes in the disc members and retaining them injuxtaposed concentric relatively rotatable relation.

2. A navigation instrument as set forth in claim 1 and also comprisingat least one further disc member concentrically pivoted to said basemember and smallerthan and overlying said third disc member, each ofsaid further disc members being marked on its periphery with a pair oflubber line arrows apart, each pair representing the direction of anavigational vector.

3. A navigational instrument as set forth in claim 1 and furthercomprising two protractor arms of transparent material mounted on saidpivot means over said disc members for independent rotation, each ofsaid arms having a straightedge eligned with the pivot axis and markedtherealong with sets of distance scales; one of said arms bearing adegree scale concentric with the pivot axis and the other of said armshaving index means for reading against said last named degree scale theangle between said straight edges.

1. A navigation instrument comprising in combination: a transparent flatbase member having a central pivot hole and inscribed with a set ofrectangular grid lines, a set of lines extending radially of said pivotcenter toward the periphery of the base member and providing thedivisions of a full circular angle scale numbered in nautical points, alubber line mark and a diametrically opposite index mark on said scale,and two arcuate degree scales inwardly of said circular scale andconcentric therewith, extending from respective zero points at 45* tothe left and right of said lubber line mark; a first disc memberconcentrically pivoted to said base member and of radius less than saidcircular angle scale and overlying said arcuate degree scale and markedat its periphery with a scale graduated in degrees including a zero markto which magnetic variation may be referred and having two symmetricallyplaced cutouts at 45* right and left of its said zero mark and at aradial distance from said pivot hole for reading on respective ones ofsaid arcuate scales the relative displacement of said first disc memberand said base member; a second disc member concentrically pivoted tosaid base member and overlying the central circular area of said firstdisc member that is inwardly of the cutouts in said first disc member,said second disc member being marked with a peripheral scale graduatedin degrees and having a zero point to which magnetic compass deviationmay be referred, and said second disc member having two arcuate degreescales inwardly of the peripheral scale thereon and concentric therewithand extending from respective zero points at 45* left and right of saidzero point of said peripheral scale thereon; a third disc memberconcentrically pivoted to said base member and overlying a centralcircular area whose periphery is between said peripheral scale on saidsecond member and said two arcuate scales thereon, said third discmember being marked with a compass rose comprising a peripheral scalegraduated in degrees, and having two symmetrically placed cutouts at 45*right and left of the north point of said compass rose and at a radialdistance from said pivot hole for reading on respective ones of saidarcuate scales on said second disc the relative displacement of saidthird disc and said second disc; and a pivot element extending throughthe pivot hole in said base member and through coaxial pivot holes inthe disc members and retaining them in juxtaposed concentric relativelyrotatable relation.
 2. A navigation instrument as set forth in claim 1and also comprising at least one further disc member concentricallypivoted to said base member and smaller than and overlying said thirddisc member, each of said further disc members being marked on itsperiphery with a pair of lubber line arrows 180* apart, each pairrepresenting the direction of a navigational vector.
 3. A navigationalinstrument as set forth in claim 1 and further comprising two protractorarms of transparent material mounted on said pivot means over said discmembers For independent rotation, each of said arms having astraightedge eligned with the pivot axis and marked therealong with setsof distance scales; one of said arms bearing a degree scale concentricwith the pivot axis and the other of said arms having index means forreading against said last named degree scale the angle between saidstraight edges.